Sorry but I can’t help you much on this one. I can’t make sure that every plugin is compatible with the theme, especially those that aren’t even available on the official WordPress repository. There’s probably a good reason why it got removed.
Though the only thing I could think of that might affect that plugin is frontier slider’s script. You could try deactivating the slider if it’s enabled. Another issue could be caching. If you have any plugins like that, try to refresh the cache. If it still doesn’t work and you’re quite sure that Frontier Theme is the cause then you’ll have to find another theme.